Drinking water, also known as potable water or improved drinking water, is water that is safe to drink or to use for food preparation, without risk of health problems. Globally, in 2015, 91% of people had access to water suitable for drinking. Nearly 4.2 billion had access to tap water while another 2.4 billion had access to wells or public taps. 1.8 billion people still use an unsafe drinking water source which may be contaminated by feces. This can result in infectious diarrhea such as cholera and typhoid among others. Water is essential for life. The amount of drinking water required is variable. It depends on physical activity, age, health issues, and environmental conditions. It is estimated that the average American drinks about one litre of water a day with 95% drinking less than three litres per day..source:wikipedia
